Overall, it's quite a fun story, with a premise that isn't too unusual for the series. There are some iffy spots in the grammar, but nothing too jarring. Only other gripe would be that Hermione should have finished her dump before the end. The way it goes, it just sort of stops like "That's it.", it's just abrupt.
I'm with Orpheum, no one likes walls 'o text.
edit the format and I'll happily read it
Whoa, big block. I'm sorry, but it'd give me, and likely anyone else a headache to try and read this.
I'd advise going back and breaking it up into paragraphs. A general rule of thumb I know is to break every 4 periods, of course if the sentence or 'part' requires more, then it's fine.
Trust me, it'll be much easier for people to read and understand.